Inside a Kansas greenhouse, a buzzing horde of flies set about laying waste to 20,000 seedlings. But as researchers watched, there was one species of growth that remained untouched – an ancient Syrian grass known as Aegilops tauschii.

From 2000 to 2015, average temperatures in the US midwest rose from 1 to 2 degrees fahrenheit above the 20th-century average. Periods of time between rainfalls are lengthening, according to a 2016 assessment by the Environmental Protection Agency. In other words, conditions in some areas of the midwest are starting to resemble conditions in the Middle East.

Rising temperatures are already leading to drops in midwestern crop yields, and threaten further reductions of as much as 4% per year. In the heart of US cereal and grain country, new pests and diseases are following the hot and dry conditions northward – and frequently overwhelming the ability of agricultural chemicals to battle them off. In response, scientists are seeking sources of natural resistance – and finding them in Syria, in the heart of the Fertile Crescent, the birthplace of domesticated agriculture.

One of the world’s most important seed banks used to be located about 25 miles west of Aleppo in the town of Tal Hadya, and was run by the International Center for Agricultural Research in the Dry Areas (Icarda). That UN-affiliated centre specialises in preserving and researching seeds in hot, dry areas – conditions now being faced by many of the Earth’s food-growing regions.

It’s also the place of origin of today’s domesticated wheat, and the seeds that were stored there benefit from genes embedded with survival strategies evolved over thousands of years. Now diseases and pests such as the Hessian fly, long familiar to Middle and Near Eastern farmers, are moving north from the southern US and Mexico and surging across Kansas and surrounding states – Oklahoma, Texas, Colorado and Nebraska and in some instances up to Illinois and the Dakotas.

Even as forces supporting the Syrian president, Bashar al-Assad, were bombing Aleppo in spring 2016, researchers at Kansas State University (KSU) were receiving increasingly urgent reports from US wheat farmers of devastating attacks by the Hessian fly, leading to an average 10% yield loss per year, according to the Feed the Future Innovation Lab for Applied Wheat Genomics at KSU. That’s a significant bite out of the earnings of farms already operating on shaky margins.

Ming-Shun Chen, a professor of molecular entomology at KSU, says the flies’ larvae used to be killed off by the cold of winter. But that cold is coming later in the season, and the larvae survive to turn into flies. Their devouring of wheat seems drawn from science fiction: the flies don’t have teeth, so they inject a protein-based substance into the plant that transforms it into a kind of nutritious slurry they can suck up and digest.

From November through April, Chen collaborated with the plant scientist Jesse Poland to run a sequence of experiments that unfolded in the university’s greenhouses with brutal Darwinian efficiency: they planted commercial US wheat seedlings from Kansas and surrounding states along with an assortment of wild wheat-related grasses obtained from the seed vault in Syria, as well as random other assorted plantings. The seedlings grew for two to three weeks, and then the flies were unleashed to attack. The results were clear: Syria’s Aegilops tauschii was the sole survivor.

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Wheat has the most complex genome of any of the world’s major crops, one of the reasons efforts to genetically engineer wheat traits have thus far not succeeded. It also means it has multiple genetic “wild relatives”.

Over time the domesticated wheat, dependent on agrichemical boosters, lost resistance to diseases and pests. So breeders are reaching deep into the history of wheat to bring back some of those lost characteristics.

“Wild relatives are by definition hardier. They’ve survived on the margins of our pampering,” says Maywa Montenegro, a PhD in environmental science, policy and management at the University of California, Berkeley, who has spent years studying wild relatives of crops. “On a farm, the farmer does everything to favour his crops: he pulls out competitor plants, weeds, gives water. But the wild relatives haven’t been getting assistance for thousands of years. They’re dealing with drought and flooding and salt.”

She said indigenous farmers have for millennia encouraged wild species to grow along the edges of their farms in order to encourage interbreeding between the wild and domesticated species to confer those strengths – a practice that has been long-neglected on massive industrial farms.

The indomitable Aegilops tauschii grows wild in Syria in the hills surrounding Tal Hadya and Aleppo. Poland cites a litany of diseases to which the grass is resistant, with names like a lineup of underground rock bands: barley yellow dwarf, mosaic virus, wheat rust. It also shows resistance traits to more than half a dozen common insect pests, including the Hessian fly.

The tauschii and thousands of other seed varieties once stored at Icarda’s Tal Hadya seed bank have a dramatic recent history, intertwined with the Syrian civil war. The area around Aleppo was a rebel stronghold until 2016. The rebel commander in Tal Hadya, according to one of the veteran scientists who used to work at the Icarda facility, was himself a farmer and understood the importance of the seed bank.

The scientists and the rebels struck a deal: the rebels protected the seed bank and, equally important, ensured that the generator kept running to keep the stored seeds cool – in return for the scientists providing the rebels with food grown from the centre’s experimental fields. That lasted until spring 2016, when Assad’s military started bombarding Aleppo and the surrounding towns, including Tal Hadya. The remaining scientists loaded up the seeds in a truck and raced across the Lebanese frontier.

Other seeds emanating from Syria are helping farmers contend with climatic changes elsewhere in the midwest. In Illinois and the Dakotas, Syrian seeds seem to perform strongly when faced with the combination of increasing temperatures with brief but intense rainfalls, which leads to the spread of virulent fungus. Efforts are under way at the University of North Dakota, Bismarck, to introduce Syrian seeds into the breeding stock.

Poland says the latest round of Hessian fly experiments, completed in early April, affirmed KSU’s plan to incorporate the tough survivors of the fly onslaught into the breeding of commercial American wheat varieties. After undergoing formal certification and government approval, the Aegilops tauschii will be dispersed to US breeders to make their way into the besieged fields of the midwest.

The US has been losing diversity at an alarming rate during more than three decades of consolidation in the seed industry, and the steadily expanding size of farms. Diversity in seed varieties has dropped in almost every region of the country, most dramatically in the lower midwest. Globally, the UN has declared that three-quarters of all the world’s crop varieties that were around in the early 1900s had become extinct by 2015.

“You may be using wild crop relatives to boost industrial agriculture, while industrial agriculture itself is one of the greatest pressures on their existence,” says Montenegro. “They’re threatened from the usual pressures – pollution, land-cover changes – but also from turning diverse fields into monoculture plantations.”